1. Field of the Invention
This invention relates to a room temperature-curable polyorganosiloxane composition. More specifically, this invention relates to a room temperature-curable polyorganosiloxane composition whose cured surface is difficult to soil and which does not soil a substrate which has been brought into contact with the cured composition.
2. Background Information
Room temperature-curable polyorganosiloxane compositions and particularly polyorganosiloxane compositions which can be cured at room temperature into a rubbery material are conventionally used in a broad range of applications such as electric insulating materials, barrier materials, for sealing containers, and as sealants. However, when such a room temperature-curable polyorganosiloxane composition is employed as above, it readily adheres or adsorbs dust. In particular, when it is employed as a construction sealant on a building exterior, liquid polyorganosiloxane gradually migrates from the cured silicone rubber to the surrounding building wall where it becomes soiled, resulting in a deteriorated external appearance for the building. This is a defect of many prior art room temperature-curable polyorganosiloxane compositions. Methods for eliminating this defect have been proposed in which a surfactant such as a polyoxyalkylene compound or its polyorganosiloxane copolymer is added to the composition such as referred to in Japanese Kokai Pat. No. 56-76453(81-76453), published June 24, 1981, and Japanese Kokai Pat. No. 56-76452(81-76452), published June 24, 1981.
However, the addition of a surfactant significantly reduces the adhesiveness, which is indispensable in a sealant to be used for buildings, and, furthermore, this strategy does not satisfactorily prevent soiling.
Various methods were examined by the present inventors in order to eliminate the defect of easy soiling in prior art room temperature-curable polyorganosiloxane compositions and this invention was developed as a result.